This error happens to me systematically, with whichever one of my three cameras I use: whenever I import photos along with one or multiple videos in the same folder, the import seems to stall. Whenever I eventually cancel the import, I get the following message:
"No photos or videos were found to import."
After that, if I remove the videos from the folder to be imported, the import is successful. But then of course, my videos are not managed in Lightroom along with the photos.